Yes I know days are maybe a tad bit colder and shorter but I wouldn’t
think there would be that much difference.
Neither would I!
1) Baltic: after cruise, stay an extra night probably in St.
Petersburg on our own. Stay near the train station to Tallin. Anybody
know what that train station is called? Everybody seems to think St.
Petersburg is worth more time and then we can leave the next morning
very early on the train to Tallinn. I think it currently leaves at
6:25 am And arrives at 12:45 pm.
According to the Man in Seat 61, the train to Tallinn leaves Moskovski station. But you might need to check the schedule, as far as I know there are only night trains on that route. A faster option is to take the train to Helsinki and a ferry from there. (I'm sure it was just a mistake, but the Estonian capital is spelled Tallinn with two Ns. Tallin is the russian spelling that was used during the Soviet occupation. I don't mean to be nitpicking, but this is an instance where spelling is important.)
Then fly to Helsinki for a night or two and fly home to Florida. In
order to get the free airfare we have to fly from Helsinki (though we
must pay a $100 each deviation fee). None of the Baltic countries are
part of the fly free deal.
I'm not saying this because I'm Swedish, but if Stockholm and Copenhagen are included in the fly free deal, I think one of them would be a better choice. And you can easily add a night or two in Helsinki between St Petersburg and Tallinn. From Vilnius it is roughly the same distance to Stockholm and Helsinki, while Copenhagen is a bit further away (but probably only 10 minutes or so by plane).
2). Scandinavia: After cruise, train to Helsinki. Stay one night. Take
overnight ferry to Stockholm. Everybody talks about how beautiful the
first few hrs of this trip are via ferry but wouldn’t it be too dark
to see anything cause I think it leaves at 5 pm?...
In early September it will not be dark when you depart and arrive. I did a quick check, on the 6th the sun sets 20:11 in Helsinki and rises 05:58 in Stockholm on the 7th. So you will see the best views (and a sunset over the Baltic sea).
and I think the ferry only goes about 3 times per week so we may need
to stay awhile longer in St. Petersburg or Helsinki.
There are two companies (Viking and TallinkSilja) that both have daily departures between Stockholm and Helsinki, at least when there is no pandemic.
Is there any way to go directly from St. Petersburg-Stockholm other
than flying which, if you want a cheap flight, is a horrible schedule.
St Peterline has direct overnight ferries between St Petersburg and Stockholm but only once or twice per week in the summer, and in September I guess it would be once weekly at most. Regarding flights I don't think the schedule for autumn 2021 has been set yet so it's hard to say if it will be horrible or not.
Stockholm 3 nights, Then train or bus or flight to Oslo 3 nights (or
skip Oslo cause it seems to be out of the way) and then train/bus/fly
to Copenhagen 3 nights. Fly home from copenhagen.
Don't get me wrong, I love Oslo. But the main attraction in Norway is the nature. And as much as I love Oslo, I'm not sure it is worth the detour (but if you go, you will probably have a great time!). Another option is to add a bit of time to a day trip or two from one of the cities, or a stop along the way. I can't help but thinking that both your schedules are very focused on the capitals.